This invention relates to a wellbore treatment to minimize polymer plugging thereby permitting extended polymer injection in enhanced oil recovery processes. The process includes treatment with organic cation containing materials which exchange with inorganic ions on the rock in the formation which would otherwise interact with polymer. Representative ions include sodium, potassium, calcium, magnesium, etc.
The organic cation which interacts with the rock can have ammonium, pyridinium, sulfonium, or oxonium ion.
The general group of compounds included within this invention have previously been injected into rock formations for other purposes.
An example of this is Brown, U.S. Pat. No. 2,761,835 (1956), which was directed to the maintenance and/or restoration of permeability of clay containing rock to fluids and the use in a wellbore is shown. The reaction is quite different in that patent since the additive serves to reduce the swelling effect of water, water having a known ability to cause clays to swell. Clay can have cations in the base-exchange position or site including by way of example, sodium, potassium, calcium, magnesium, iron, hydrogen, etc. This patent suggests the treatment of the clay with primary, secondary, tertiary, and quaternary ammonium halides, the chloride being particularly identified.
Another example is Dreher, et al., U.S. Pat. No. 3,830,302 (1974), a patent directed to the reduction in the water-oil-ratio of producing wells. This reduction can be effected by injecting a polyacrylamide solution and a organic cation, e.g., alkyl trimethalamonium halide, a sulfonium compound or a pyridinium compound. Also disclosed is injecting the polymer with subsequent treatment with the cation containing compound.
Further, is Knox, et al., U.S. Pat. No. 3,794,117 (1974), which is directed to the treatment of sandstone formations with aqueous acid solutions. It is said that addition of a cationic nitrogen containing compound can be used to improve the penetration of the acid by reducing its effect near the wellbore.
The following are objects of this invention.
An object of this invention is to provide a new method for treating wellbores to reduce polymer formation plugging. In a more specific aspect, an organic cation containing material is injected into the formation to exchange with inorganic ions on the rock surface which would otherwise interact with the polymer and cause plugging.
Other objects and advantages of this invention will be apparent to one skilled in the art upon reading this disclosure.